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RE: Snow Drift from BOCA 1978 or 1981

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Portion of '81 Code to be faxed to you.  Unless you just happen to be
checking an existing condition for code compliance at the time it was
constructed you need to design the existing structure based on current codes
if effected by new alterations. Also remember that there were significant
increases in the minimum ground snow under BOCA 1985.

Matthew Stuart, PE, SE, PEng.
Atlantic Engineering Services
Pittsburgh

 -----Original Message-----
From: 	Hyndman, Keith [mailto:KHyndman(--nospam--at)engineeringsi.com]
Sent:	Tuesday, May 29, 2001 10:21 AM
To:	'seaint(--nospam--at)seaint.org'
Subject:	Snow Drift from BOCA 1978 or 1981

Greetings all.

Does anyone out there have access to BOCA 78 or 81?  I'm interested in the
Snow Drift requirements on lower level roofs for multi-level roof building.

I have a copy of BOCA 84 the formula is as follows:

                                Cs=15*h/g

                                Cs min = 0.8
                                Cs max = 3.0
                                h = Difference of roof heights
                                g = ground snow load (from 25,50,100 yr
maps)

                                Drift = Cs*g

I'm having a "discussion" with an Architect who insists on putting 2 story
buildings right next to single story buildings.

In this particular case I'm looking at a set of drawings from 1983 were this
was done and the lower roof (good for about 50psf) was "not" reinforced.
According to BOCA 99 the max drift load would be about 90 psf on the lower
roof.  So the Architect wants to put another 2 story on the other side of
the building, and wonders "What's all the fuss!"

So before I approach the owner with the information that his existing roof
is not adequate by today's standards, I want to see if the original design
was flawed.

Thank for your input.

Keith Hyndman, P.E.
khyndman(--nospam--at)engineeringsi.com
Engineering Solutions Inc.
436 Creamery Way, Suite 100
Exton, PA 19341
Phone: 610-524-1357
Fax: 610-524-1317


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